Buggy code:
public class SolrCmdDistributor { private static final int MAX_RETRIES_ON_FORWARD = 15 ; public static Logger log = LoggerFactory . getLogger ( SolrCmdDistributor . class ) ; static AdjustableSemaphore semaphore = new AdjustableSemaphore ( 8 ) ; CompletionService < SolrCmdDistributor . Request > completionService ; Set < Future < SolrCmdDistributor . Request > > pending ; int maxBufferedAddsPerServer = 10 ; int maxBufferedDeletesPerServer = 10 ; private SolrCmdDistributor . Response response = new SolrCmdDistributor . Response ( ) ; private final Map < SolrCmdDistributor . Node , List < SolrCmdDistributor . AddRequest > > adds = new HashMap < SolrCmdDistributor . Node , List < SolrCmdDistributor . AddRequest > > ( ) ; private final Map < SolrCmdDistributor . Node , List < SolrCmdDistributor . DeleteRequest > > deletes = new HashMap < SolrCmdDistributor . Node , List < SolrCmdDistributor . DeleteRequest > > ( ) ; private UpdateShardHandler updateShardHandler ; class AddRequest { AddUpdateCommand cmd ; ModifiableSolrParams params ; } class DeleteRequest { DeleteUpdateCommand cmd ; ModifiableSolrParams params ; } public static interface AbortCheck { public boolean abortCheck ( ) { } } public SolrCmdDistributor ( int numHosts , UpdateShardHandler updateShardHandler ) { } public void finish ( ) { } public void distribDelete ( DeleteUpdateCommand cmd , List < SolrCmdDistributor . Node > urls , ModifiableSolrParams params ) throws IOException { } public void distribAdd ( AddUpdateCommand cmd , List < SolrCmdDistributor . Node > nodes , ModifiableSolrParams params ) throws IOException { } public void syncAdd ( AddUpdateCommand cmd , SolrCmdDistributor . Node node , ModifiableSolrParams params ) throws IOException { } public void syncDelete ( DeleteUpdateCommand cmd , List < SolrCmdDistributor . Node > nodes , ModifiableSolrParams params ) throws IOException { } private void syncRequest ( SolrCmdDistributor . Node node , UpdateRequestExt ureq ) { SolrCmdDistributor . Request sreq = new SolrCmdDistributor . Request ( ) ; sreq . node = node ; sreq . ureq = ureq ; String url = node . getUrl ( ) ; String fullUrl ; if ( ( ! ( url . startsWith ( "http:////" ) ) ) && ( ! ( url . startsWith ( "https:////" ) ) ) ) { fullUrl = "http:////" + url ; } else { fullUrl = url ; } HttpSolrServer server = new HttpSolrServer ( fullUrl , updateShardHandler . getHttpClient ( ) ) ; try { sreq . ursp = server . request ( ureq ) ; } catch ( Exception e ) { <START_BUG> throw new org . apache . solr . common . SolrException ( ErrorCode . SERVER_ERROR , ( "Failed<seq2seq4repair_space>synchronous<seq2seq4repair_space>update<seq2seq4repair_space>on<seq2seq4repair_space>shard<seq2seq4repair_space>" + ( sreq . node ) ) , sreq . exception ) ; <END_BUG> } } public void distribCommit ( CommitUpdateCommand cmd , List < SolrCmdDistributor . Node > nodes , ModifiableSolrParams params ) throws IOException { } private void doDelete ( DeleteUpdateCommand cmd , List < SolrCmdDistributor . Node > nodes , ModifiableSolrParams params ) { } void addCommit ( UpdateRequestExt ureq , CommitUpdateCommand cmd ) { } boolean flushAdds ( int limit ) { } boolean flushDeletes ( int limit ) { } private DeleteUpdateCommand clone ( DeleteUpdateCommand cmd ) { } public static class Request { public SolrCmdDistributor . Node node ; UpdateRequestExt ureq ; NamedList < Object > ursp ; int rspCode ; public Exception exception ; int retries ; } void submit ( UpdateRequestExt ureq , SolrCmdDistributor . Node node ) { } public void submit ( final SolrCmdDistributor . Request sreq ) { } public static Callable testing_errorHook ; void checkResponses ( boolean block ) { } public static class Response { public SolrCmdDistributor . Request sreq ; public List < SolrCmdDistributor . Error > errors = new ArrayList < SolrCmdDistributor . Error > ( ) ; } public static class Error { public SolrCmdDistributor . Node node ; public Exception e ; } public SolrCmdDistributor . Response getResponse ( ) { } public abstract static class Node { public abstract String getUrl ( ) { } public abstract boolean checkRetry ( ) { } public abstract String getCoreName ( ) { } public abstract String getBaseUrl ( ) { } public abstract ZkCoreNodeProps getNodeProps ( ) { } } public static class StdNode extends SolrCmdDistributor . Node { protected ZkCoreNodeProps nodeProps ; public StdNode ( ZkCoreNodeProps nodeProps ) { } @ Override public String getUrl ( ) { } @ Override public String toString ( ) { } @ Override public boolean checkRetry ( ) { } @ Override public String getBaseUrl ( ) { } @ Override public String getCoreName ( ) { } @ Override public int hashCode ( ) { } @ Override public boolean equals ( Object obj ) { } @ Override public ZkCoreNodeProps getNodeProps ( ) { } } }

Fix:
throw new org . apache . solr . common . SolrException ( ErrorCode . SERVER_ERROR , ( ( ( "Failed<seq2seq4repair_space>synchronous<seq2seq4repair_space>update<seq2seq4repair_space>on<seq2seq4repair_space>shard<seq2seq4repair_space>" + ( sreq . node ) ) + "<seq2seq4repair_space>update:<seq2seq4repair_space>" ) + ureq ) , e ) ;